Join Date: Jan 2007
Location: Palmer Lake, Colorado
Gas mileage way up!
Here's one for you all to chew on... Long post, bear with me in advance.
I am a bit miffed myself, but because I keep pretty thorough records of stuff, I know the below is real, but HOW?
Put new chain and sprockets on in late May (03 Vee). Went from 17/42T gearing to 17/41t. Did a road trip to Moab, Utah and back from my home in Palmer Lake, Colorado right after the change. A little over 45 mpg average for 900 miles. Keep in mind, changing the gearing changes the odometer's accuracy. I checked with my GPS and the 17/41 combo gives me a 1% error (shows more miles than I actually travel) and with the 17/42 combo I had a 4% error calculated by the same method. So, I always adjust my miles travelled to account for the error when figuring actual gas mileage.
About 500 miles ago, I adjusted the valves and set them to middle of spec on exhaust (all were at minimum spec, tight) and based on the shims available, set the intakes to .007 (.004-.008 spec, and all were at .004 or .005, tight like the exhaust valves).
Also put my K&N air filter back in at the time of valve adjustment, after changing back to the stock filter last fall. I ran the K&N for a couple thousand miles previously but pulled it out when I felt the driveability was being affected (the dreaded surging). Saw no difference in MPG previously with the K&N. Got the TFI dialed in real well now, so went back to the K&N to see if I had any issues, and I don't. Runs great.
Last week took a 190 mile round trip up to Boulder for work. Mileage was 49.5mpg. Next, ran 125 miles back and forth to work (35 mile round trip) and running errands. Filled up last night, 47.6 mpg. Went up to Fort Collins and Greeley today for work, 270 mile round trip. 50.5 mpg for this trip. Fillling up at the same pump, facing the same direction, filling it to the same point in the filler neck, you get the idea.
I have done all these runs before adjusting the valves and putting the K&N back in, and average 44 mpg on the work commute round trip, and never better than 46 mpg on the Boulder or Fort Collins run.
Anyway, thought I'd share and if any of you are thinking of a valve adjustment and it's over due, might not be a bad idea!